The present invention is generally directed to processes for the preparation of resin coated particulate materials, for example, carrier particles especially for use in two component xerographic developers. More specifically, the present invention relates to improved dry powder coating processes for the preparation of polymer coated porous metal oxide core particles.
The present invention relates to processes for the preparation of polymer coated carrier particles, and more specifically dry powder coating processes for the preparation of polymer coated porous particles comprising relatively small sized metallic sponge carrier particles, with a first coating thereover comprised of a first polymer material of relatively low cost, for example, less than about 1 to about 3 dollars (U.S.) per pound which functions primarily as a filler, a mechanical stability enhancer, or as a sacrificial material, and a second coating thereover comprised of a second polymer or mixture of polymers with a relatively higher cost, for example, for about 3 to about 20 or more dollars (U.S.) per pound and having superior triboelectric charging and/or conductive properties compared to the first polymer coating material.
Dry polymer coating processes for carrier particles are known in the art, such as U.S. Pat. No. 3,590,000 (Mammino, et al.), U.S. Pat. No. 4,233,387 (Mammino, et al.), U.S. Pat. No. 4,935,326 (Creatura, et al.), U.S. Pat. No. 4,937,166 (Creatura, et al.), and U.S. Pat. No. 5,002,846 (Creatura, et al.).